20 Injuries in Pregnancy

20

Injuries in Pregnancy

Paul D. Wallman and Adam J. Brooks

418

Introduction

Trauma is an increasing cause of morbidity and mortality in pregnancy, accounting for approximately seven percent of maternal fatalities, and is the most common case of non-obstetric maternal death. Even minor trauma can result in serious fetomaternal complications, including premature labor, placental abruption, and fetal injury. In most communities, blunt trauma accounts for the majority of injuries in pregnant women; however, in some series, penetrating trauma is responsible for 20% of the injuries seen in pregnant patients.

As pregnancy progresses, a series of specific anatomical and physiologi- cal adaptations occur that bring with them altered injury patterns, unique complications, and a change in the response to injury. It is essential that those involved in the management of ballistic injury in a pregnant patient understand these changes so that appropriate care can be provided for both the mother and her unborn child.

All female trauma victims of child-bearing age must be considered to be pregnant until proven otherwise.

Relevant Anatomy and Physiology of Pregnancy

The most striking anatomical alteration during pregnancy is the develop-

ment of the uterus from a pelvic organ in the non-pregnant female to an

intra-abdominal organ as the pregnancy develops. By the twentieth week,

when the uterus has reached the umbilicus, the abdominal viscera are dis-

placed up toward the diaphragm and the uterus becomes exposed to the

same hazards as the intraperitoneal structures. As the pregnancy progresses,

the uterus shields the mother from penetrating trauma, with the incidence

of maternal organ damage following gunshot wounds being quite low. At

this stage, the uterus is thin walled, the amniotic fluid volume is decreased,

and the full-term pregnant uterus is highly vulnerable to ballistic trauma.

A series of physiological adaptations occur during pregnancy that may complicate the resuscitation and can alter the physiological response to injury.

Cardiovascular System

– 50% increase in plasma volume

– slight increase in hemoglobin, but not as marked as the plasma volume, therefore the hematocrit is decreased (physiological anemia of pregnancy)

– increase in cardiac output by 1.0 to 1.5 liters per minute – increase in heart rate by 5 to 15 beats per minute

– 5 to 15 millimeters Hg decrease in blood pressure during the second trimester, returning to normal by term

– during the later stages of pregnancy, in the supine position, the gravid uterus can compress the inferior vena cava, reducing the venous return and hence cardiac output (supine maternal hypotension)

The maternal volume expansion allows for a greater absolute volume loss, up to 1.5 liters, prior to signs of maternal shock, although the fetus may already be in distress.

Respiratory System

– hyperventilation due to increased oxygen requirements – 50% increase in tidal volume and minute ventilation – functional residual capacity is reduced

– partially compensated respiratory alkalosis

The other organ systems are also affected during pregnancy. Displace- ment of the abdominal viscera leads to delayed gastric emptying and failure of the lower esophageal sphincter. This combination increases the risk of aspiration of stomach contents.

Initial Assessment and Management

The initial assessment and management of the pregnant patient with bal- listic injury should follow the doctrine provided throughout this book. In order to optimize the outcome of both mother and fetus, it is essential to assess, identify, and resuscitate the mother first, and then subsequently address the needs of the fetus. Early consultation with an obstetrician is vital to the outcome of both patients.

The adaptations of pregnancy described previously can alter the patterns

and manifestation of injury. The alterations that have a potential impact on

the resuscitation of the pregnant patient are highlighted below.

Airway

– There is an increased risk of aspiration due to gastric reflux and delayed gastric emptying; therefore, the stomach should be decompressed early with a nasogastric tube.

– Endotracheal intubation can be complicated by edema of the neck or epiglottis.

Cervical Spine Control

– Cervical spine management remains as detailed in the chapters on pre- hospital care and spinal injury.

Breathing

– The pregnant patient is resuscitated in the standard way and high-flow oxygen should be administered to ensure a high FiO

.

Circulation

– Due to an increased circulatory volume, the mother may compensate for a long period before signs of hypovolemia become apparent.

– The utero-placental circulation will be sacrificed to maintain the mother’s cardiovascular status. The fetal circulation will therefore be reduced and may result in a poor fetal outcome.

– Early intravenous access and volume replacement are essential prior to definitive control for minimal morbidity and mortality to the patient and fetus.

– These procedures should not delay early surgical intervention or early cesarean section when required (see Surgical and Obstetric Intervention).

The maternal physiological preference may result in the fetus being in shock while the mother’s cardiovascular vital signs and condition remains stable.

– Supine maternal hypotension exacerbates cardiovascular compromise. In the absence of spinal injury requiring immobilization, the patient can be managed in the left lateral position; alternatively, the right pelvis can be tilted upwards on a spinal board or with a rolled towel. Otherwise an individual can be allocated to manually displace the uterus to the patient’s left-hand side, thus holding the uterus “off” the inferior vena cava (IVC).

In addition to the usual blood tests, serum beta human chorio- gonadotrophin and analysis for the Rhesus antibody should be performed.

Full monitoring of the mother’s physiological parameters is required and

electronic fetal monitoring is an essential adjunct if available.

Assessment of the Pregnant Abdomen

The change in position of the intra-abdominal organs that occurs as preg- nancy progresses must be considered when abdominal ballistic wounds and likely injury patterns are being evaluated. As part of the abdominal exami- nation, a thorough examination of the perineum, vagina, and rectum must be performed, in addition to an assessment of the uterus and upper abdomen.

Free drainage of clear amniotic fluid, cervical dilatation, fetal presentation, and concealed or occult bleeding must be excluded. Rectal examination may add information regarding bowel, uterine/fetal, and pelvic injury.

Investigations

In ballistic trauma to the abdomen, little investigation is usually required, as laparotomy is usually indicated; however, ultrasound is a useful diag- nostic tool in the evaluation of the pregnant abdomen, as it can be used to assess for fetal well being and intrauterine pathology, as well as intra- abdominal bleeding. CT can also be considered where trajectory is in doubt in the stable patient in the late stages of pregnancy.

If peritoneal penetration is truly in doubt, diagnostic peritoneal lavage may rarely be used to guide the decision for laparotomy, but it is invasive and should be performed well above the umbilicus by an experienced surgeon.

Plain radiography is indicated as for the non-pregnant patient; however, the minimum number of X-rays should be performed to obtain maximum information. Bullet markers can be used to help determine uterine pene- tration and therefore the chance of fetal injury.

A Pinnard’s stethoscope or Doppler fetoscopy should be immediately available to identify the presence of a fetal heartbeat. Continuous electronic fetal heart-rate monitoring is the modality of choice in most institutions and provides information on the fetal heart rhythm, including abnormal rate, decelerations, accelerations, and beat-to-beat variability. A normal fetal heart-rate pattern has at least a 95% correlation with good fetal perfusion.

Surgical and Obstetric Intervention

Early involvement of an experienced surgeon and obstetrician is central to the reduction of morbidity and mortality in these patients. Risk assessment involves balancing the well being of the mother versus the well being of the fetus. In addition, fetal well being must be assessed in terms of the risk in utero versus the risk of premature delivery.

As pregnancy progresses, the bowel is displaced and compressed upwards

by the uterus, making it vulnerable to gunshot wounds to the upper

abdomen and liable to multiple perforations. The enlarged uterus acts as a

shield for the mother; lower abdominal wounds nearly exclusively involve the uterus and its contents, which act to absorb the energy of the missile.

This clearly places the fetus in jeopardy; gunshot wounds to the uterus are associated with a fetal mortality of 70%, with a maternal mortality of less than ten percent. Fetal survival following ballistic injury is also dependent on gestation, with gestations less than 37 weeks having much worse survival.

Extra-uterine abdominal ballistic injuries are managed as previously dis- cussed in this book, although in the later stages of pregnancy the uterus can impede access and mobilization of the viscera. Abdominal injuries and the need for a laparotomy do not alone justify cesarean section (c-section).

Urgent c-section has only been recommended in cases of severe maternal shock in near-term pregnancies, fetal distress in excess of the risk of pre- mature delivery, exsanguinating injury, and unstable thoracolumbar spine injury.

Ballistic Injuries in the Pregnant Patient:

Special Considerations

All torso ballistic injuries in the pregnant patient may give rise to spillage of fetal blood into the maternal circulation. If the fetus is Rhesus antibody positive and is being carried by a Rhesus antibody negative mother, then there is the potential for maternal sensitization to occur even with minimal volume. Isoimmunization, the production of antibodies against the Rhesus positive fetus, can result, and appropriate treatment should be considered all cases.

Post-mortem cesarean section is only justified where there is a viable (greater than 26 week gestation) fetus and the mother is dead or moribund.

Under optimal conditions, there is a 40 to 70% chance of fetal survival without major disability. However, as the elapsed time increases, the chance of survival falls and 70% of surviving infants will be delivered within five minutes of maternal death.

Summary

All members of the trauma team must appreciate the unique differences in caring for the pregnant victim of ballistic trauma.

– All female trauma victims of child-bearing age must be considered to be pregnant until proven otherwise.

– Early involvement of both a surgeon and obstetrician is required to min- imize morbidity and mortality in both patients.

– Members of the trauma team should have a basic knowledge of the

anatomical and physiological alterations that occur in pregnancy.

– The initial trauma approach remains the same as all other patients—the mother is treated first and the fetus second.

– Rapid and meticulous assessment must exclude general life-threatening pathologies, and those injuries unique to pregnancy must be considered.

– The fetus may be in jeopardy despite apparent minor injury to the mother.

Further Reading

Buschbaum HJ. Penetrating injury of the abdomen. In: Buschbaum HJ, ed. Trauma in Pregnancy. Philadelphia: WB Saunders Co; 1979:43–87.

Franger AL, Buchsbaum HJ, Peaceman AM. Abdominal gunshot wounds in pregnancy. Am J Obstet Gynecol. 1989;160:1124–1128.

Advanced Trauma Life Support for Doctors. American College of Surgeons Com- mittee on Trauma. Student Course Manual. 6th ed. 1997:313–323.

Higgins SD. Trauma in pregnancy. J Perinatol. 1988;8(3):288–292.

Rozycki GS, Knudson MM. Reproductive system trauma. In: Felicinao DV, Moore EE, Mattox KL, eds. Trauma. 3rd ed. Stamford, CT: Appleton & Lange; 1996.

Nash P. Trauma in pregnancy. In: Skinner DV, Swain A, Robertson C, Peyton JWR, eds. Cambridge Textbook of Accident and Emergency Medicine. Cambridge, MA:

Cambridge University Press; 1997:702–707.